A module type power semiconductor device is a device integrating a main circuit, including such semiconductor chips as power transistors and diodes used for switching and other power controls, and a control circuit, including control semiconductor chips for controlling operation of the main circuit. This module type power semiconductor device is primarily used for inverters which control motors or the like.
FIG. 4 is a cross-sectional view depicting a cross-sectional structure of a conventional module type power semiconductor device. As illustrated in FIG. 4, the conventional module type power semiconductor device has a structure where a main circuit 100a and a control circuit 100b for controlling the main circuit 100a, are mounted on a same main circuit substrate 101. The main circuit substrate 101 is an insulating substrate where an insulating layer 103 is disposed on the surface of a metal plate 102, which has good thermal conductivity. A main circuit wiring pattern 104 is formed on the insulating layer 103 of the main circuit substrate 101.
Semiconductor elements constituting the main circuit 100a are formed on semiconductor chips 105 and 106. The rear surfaces of the semiconductor chips 105 and 106 are bonded with the main circuit wiring pattern 104 of the main circuit substrate 101 by a bonding material (not illustrated), such as solder. An IGBT (Insulated Gate Bipolar Transistor) and an FWD (Free Wheeling Diode) are formed respectively on the semiconductor chips 105 and 106.
A control circuit substrate 107 is an insulating substrate where a control circuit wiring pattern 108 is formed on the front surface. The control circuit substrate 107 has a via hole structure. The control circuit wiring pattern 108 and a metal film formed on the rear surface of the control circuit substrate 107 are connected by the via holes. The rear surface of the control circuit substrate 107 is bonded, by insulating adhesive 110, with the insulating layer 103 of the main circuit substrate 101 in an area where the main circuit wiring pattern 104 is not disposed.
A control semiconductor element constituting the control circuit 100b is formed on a control semiconductor chip 109. The rear surface of the control semiconductor chip 109 is bonded with the control circuit wiring pattern 108 of the control circuit substrate 107 through a bonding material (not illustrated), such as a solder. Electrodes disposed on the front surfaces of the semiconductor chips 105 and 106 (not illustrated, hereafter called “front surface electrodes”) are electrically connected with the main circuit wiring pattern 104 and the control circuit wiring pattern 108 by bonding wires 111.
A case 112 is bonded with the rim of the main circuit substrate 101. A plurality of lead terminals (lead frame) 113a and 113b used for external connection is disposed inside the case 112. One end of the lead terminal 113 used for power is exposed outside the case 112, and the other end is connected to an output electrode of the main circuit 100a by solder or the like. One end of the lead terminals 113b used for control is exposed outside the case 112, and the other end is connected to an input electrode of the control circuit 100b by a solder or the like. Sealing resin 114 fills the space between the case 112 and the main circuit substrate 101.
In such a module type power semiconductor device, the heat loss generated in the main circuit 100a must be effectively radiated to the outside of the device. In the case of the module type power semiconductor device illustrated in FIG. 4, the heat loss generated in the semiconductor chips 105 and 106 and the main circuit wiring pattern 104, which are areas where a large amount of current flows, is conducted to the metal plate 102 via the insulating layer 103. The heat loss conducted to the metal plate 102 is conducted to an external heat radiation mechanism bonded with the metal plate 102, and heat is radiated.
The semiconductor chip 109, on the other hand, is a control IC (Integrated Circuit) for generating control signals which are inputted to the semiconductor elements on the semiconductor chips 105 and 106, where only weak current flows. Therefore the control circuit substrate 107, on which the control semiconductor chip 109 is mounted, does not require a special configuration to radiate heat. As a consequence, the control circuit substrate 107 is disposed on the insulating layer 103 of the main circuit substrate 101, so as to prevent the propagation of noise generated during switching of the power semiconductor elements on the semiconductor chips 105 and 106 to the control semiconductor element on the control semiconductor chip 109. The noise prevention effect is greater as the thickness of the control circuit substrate 107 increases.
The following device has been proposed as a module type power semiconductor device (e.g. see Patent Document 1). In the module type power semiconductor device, a metal insulating substrate, semiconductor chips mounted on the metal insulating substrate, a control circuit component and external lead-out terminals are housed inside a resin case. The semiconductor chips, the control circuit component and the external lead-out terminals are internally connected by wire bonding. A partition wall that covers the upper surface of the metal insulating substrate, excluding the area where the semiconductor chips are mounted, is formed in the middle stage position in the case, and the external lead-out terminals, the control circuit component, and the wiring conductors thereof are disposed on the upper surface side of the partition plate.
Patent Document 1: Japanese Patent Application Laid-Open No. H5-304248